DSP based algorithm for non-contacting torque sensor

Abstract

A method of detecting a sensed parameter for a motor control system comprising: receiving a sensor signal, the sensor signal exhibiting a frequency responsive to an inductance of a non-contacting variable reluctance rotational displacement sensor, wherein the inductance is indicative of a displacement of the sensor and responsive to the sensed parameter; capturing a first transition of the sensor signal and a time associated therewith; capturing a second transition of the sensor signal and a time associated therewith; calculating a period for the sensor signal; and computing a value for the sensed parameter, the value responsive to the period.

1. A method of detecting a sensed parameter for a motor control system comprising:
 receiving a sensor signal, said sensor signal exhibiting a frequency responsive to an inductance and resistance of a non-contacting variable reluctance rotational displacement sensor, wherein said inductance and resistance is indicative of a displacement of said sensor and responsive to said sensed parameter;  
 capturing a first transition of said sensor signal and a time associated therewith;  
 capturing a second transition of said sensor signal and a time associated therewith;  
 calculating a period for said sensor signal; and  
 computing a value for said sensed parameter, said value responsive to said period.  
 
     
     
       2. The method of  claim 1  wherein said rotational displacement is responsive to the twist of a torsion bar. 
     
     
       3. The method of  claim 1  wherein said sensed parameter is a torque, and said inductance and resistance is responsive to said torque. 
     
     
       4. The method of  claim 1  wherein said frequency is temperature compensated. 
     
     
       5. The method of  claim 4  wherein said temperature compensation comprises computing a selected resistance for an oscillator circuit to compensate for a temperature variation of said sensor. 
     
     
       6. The method of  claim 1  further including receiving said sensor signal from an oscillator circuit. 
     
     
       7. The method of  claim 1  further including a receiving a temperature signal responsive to a temperature sensor for providing temperature compensation to said oscillator circuit. 
     
     
       8. A system for measuring a sensor parameter for a motor control system in a vehicle steering system comprising:
 a parameter sensor comprising a non-contacting variable reluctance rotational displacement sensor, generating and transmitting a sensor signal indicative of a sensed parameter;  
 a controller operatively coupled to said parameter sensor;  
 said controller executing method for: 
 receiving a sensor signal, said sensor signal exhibiting a frequency responsive to an inductance and resistance of said parameter sensor, wherein said inductance and resistance is indicative of a displacement of said sensor and responsive to said sensed parameter;  
 capturing a first transition of said sensor signal and a time associated therewith;  
 capturing a second transition of said sensor signal and a time associated therewith;  
 calculating a period for said sensor signal; and  
 computing a value for said sensed parameter, said value responsive to said period.  
 
 
     
     
       9. The system of  claim 8  wherein said rotational displacement is responsive to the twist of a torsion bar. 
     
     
       10. The system of  claim 8  wherein said sensed parameter is a torque, and said inductance and resistance is responsive to said torque. 
     
     
       11. The system of  claim 8  wherein said frequency is temperature compensated. 
     
     
       12. The system of  claim 11  wherein said temperature compensation comprises computing a selected resistance for an oscillator circuit to compensate for a temperature variation of said sensor. 
     
     
       13. The system of  claim 8  further including an oscillator circuit transmitting said sensor signal. 
     
     
       14. The system of  claim 8  further including a temperature sensor transmitting a temperature signal for providing temperature compensation to said oscillator circuit. 
     
     
       15. A steering system with a parameter sensor comprising:
 a steerable wheel coupled to a motor;  
 a parameter sensor generating and transmitting a sensor signal indicative of a sensed parameter;  
 a controller operatively coupled to said motor and said parameter sensor;  
 said controller generating command to direct said motor; and  
 said parameter sensor comprising;  
 an annular sleeve;  
 a coil coaxially aligned within said sleeve;  
 a first ring shaped toothed structure in magnetic communication with said sleeve, coaxially aligned and configured to rotate relative to said sleeve, said first ring shaped toothed structure including a first plurality of axially directed teeth arranged substantially equidistant about a circumference of said first ring shaped toothed structure on a front portion thereof;  
 a second ring shaped toothed structure in magnetic communication with said first ring shaped toothed structure and said sleeve, said second ring shaped toothed structure coaxially aligned and configured to rotate relative to said first ring shaped toothed structure and said sleeve and including a second plurality of axially directed teeth configured substantially the same as said first plurality of axially directed teeth and oriented adjacent to said first plurality of axially directed teeth on a rear portion of said second ring shaped toothed structure;  
 wherein said sleeve includes an internal flange configured to maintain a selected magnetic air gap with a rear portion of first ring shaped tooth structure; and  
 wherein said coil generates a signal responsive to a differential rotational displacement between said first ring shaped toothed structure and said second ring shaped toothed structure.  
 
     
     
       16. The steering system of  claim 15  wherein said coil substantially surrounds said first plurality of axially directed teeth and said second plurality of axially directed teeth. 
     
     
       17. The steering system of  claim 15  wherein said second ring shaped toothed structure includes a flange about its circumference configured to maintain a selected magnetic air gap with an internal surface of said sleeve. 
     
     
       18. The steering system of  claim 15  further including an oscillator circuit operatively connected with said coil, said oscillator circuit generating a frequency of oscillation responsive to said differential rotational displacement. 
     
     
       19. The steering system of  claim 15  wherein said sleeve, first ring shaped toothed structure, and second ring shaped toothed structure are fabricated from ferrite. 
     
     
       20. The steering system of  claim 15  wherein said differential rotation displacement is responsive to the twist of a torsion bar. 
     
     
       21. The steering system of  claim 15  wherein said sensor is responsive to a torque. 
     
     
       22. A system for measuring a sensor parameter for a motor control system in a vehicle steering system comprising:
 a means for receiving a sensor signal, said sensor signal exhibiting a frequency responsive to an inductance and resistance of a non-contacting variable reluctance rotational displacement sensor, wherein said inductance and resistance is indicative of a displacement of said sensor and responsive to said sensed parameter;  
 a means for capturing a first transition of said sensor signal and a time associated therewith;  
 a means for capturing a second transition of said sensor signal and a time associated therewith;  
 a means for calculating a period for said sensor signal; and  
 a means for computing a value for said sensed parameter, said value responsive to said period.  
 
     
     
       23. A storage medium encoded with a machine-readable computer program code, said storage medium including instructions for causing controller to implement a method for detecting a sensed parameter for a motor control system comprising;
 receiving a sensor signal, said sensor signal exhibiting a frequency responsive to an inductance and resistance of a non-contacting variable reluctance rotational displacement sensor, wherein said inductance and resistance is indicative of a displacement of said sensor and responsive to said sensed parameter;  
 capturing a first transition of said sensor signal and a time associated therewith;  
 capturing a second transition of said sensor signal and a time associated therewith;  
 calculating a period for said sensor signal; and  
 computing a value for said sensed parameter, said value responsive to said period.  
 
     
     
       24. A computer data signal, said computer data signal comprising code configured to cause a controller to implement a method detecting a sensed parameter for a motor control system comprising:
 receiving a sensor signal, said sensor signal exhibiting a frequency responsive to an inductance and resistance of a non-contacting variable reluctance rotational displacement sensor, wherein said inductance and resistance is indicative of a displacement of said sensor and responsive to said sensed parameter;  
 capturing a first transition of said sensor signal and a time associated therewith;  
 capturing a second transition of said sensor signal and a time associated therewith;  
 calculating a period for said sensor signal; and  
 computing a value for said sensed parameter, said value responsive to said period.  
 
     
     
       25. The method of  claim 4  wherein said frequency is temperature compensated by providing compensation for at least one of said inductance and said resistance of said sensor. 
     
     
       26. The system of  claim 11  wherein said frequency is temperature compensated with compensation for at least one of said inductance and said resistance of said sensor.